Adding splitAsList to String

Author: BalmungSan

src/main/scala/scala/next/NextStringOpsExtensions.scala

@@ -0,0 +1,49 @@
+package scala
+package next
+
+private[next] final class NextStringOpsExtensions(
+  private val str: String
+) extends AnyVal {
+  /** Split this string around the separator character; as a [[List]]
+   *
+   *  If this string is blank,
+   *  returns an empty list.
+   *
+   *  If this string is not a blank string,
+   *  returns a list containing the substrings terminated by the start of the string,
+   *  the end of the string or the separator character.
+   *
+   *  By default, this method discards empty substrings.
+   *
+   * @param separator the character used as the delimiter.
+   * @param preserveEmptySubStrings set as `true` to preserve empty substrings.
+   * @return a [[List]] of substrings.
+   */
+  def splitAsList(separator: Char, preserveEmptySubStrings: Boolean = false): List[String] = {
+    @annotation.tailrec
+    def loop(currentIdx: Int, acc: List[String]): List[String] = {
+      def addToAcc(substring: String): List[String] =
+        if (substring.isEmpty && !preserveEmptySubStrings)
+          acc
+        else
+          substring :: acc
+
+      val newIndex = str.lastIndexOf(separator, currentIdx - 1)
+      if (newIndex == -1)
+        addToAcc(substring = str.substring(0, currentIdx))
+      else
+        loop(
+          currentIdx = newIndex,
+          acc = addToAcc(substring = str.substring(newIndex + 1, currentIdx))
+        )
+    }
+
+    if (str.forall(_.isWhitespace))
+      List.empty
+    else
+      loop(
+        currentIdx = str.length,
+        acc = List.empty
+      )
+  }
+}

src/main/scala/scala/next/package.scala

@@ -12,6 +12,8 @@
 
 package scala
 
+import scala.language.implicitConversions
+
 package object next {
   implicit final class OptionOpsExtensions[A](private val v: Option[A]) extends AnyVal {
     /** Apply the side-effecting function `f` to the option's value
@@ -22,4 +24,9 @@ package object next {
      */
     def tapEach[B](f: A => B): Option[A] = { v.foreach(f); v }
   }
+
+  implicit final def scalaNextSyntaxForStringOps(
+    str: String
+  ): NextStringOpsExtensions =
+    new NextStringOpsExtensions(str)
 }

src/test/scala/scala/next/TestStringOpsExtensions.scala

@@ -0,0 +1,98 @@
+/*
+ * Scala (https://www.scala-lang.org)
+ *
+ * Copyright EPFL and Lightbend, Inc.
+ *
+ * Licensed under Apache License 2.0
+ * (http://www.apache.org/licenses/LICENSE-2.0).
+ *
+ * See the NOTICE file distributed with this work for
+ * additional information regarding copyright ownership.
+ */
+
+package scala.next
+
+import org.junit.Assert._
+import org.junit.Test
+
+final class TestStringOpsExtensions {
+  @Test
+  def splitAsListEmpty(): Unit = {
+    val str = ""
+
+    assertTrue(str.splitAsList(',').isEmpty)
+  }
+
+  @Test
+  def splitAsListBlankString(): Unit = {
+    val strings = List(
+      " ",
+      "   ",
+      "\t",
+      "\t\t\t",
+      "\n",
+      "\n\n\n",
+      " \t \t \n"
+    )
+
+    strings.foreach { str =>
+      assertTrue(str.splitAsList(',').isEmpty)
+    }
+  }
+
+  @Test
+  def splitAsListDelimiterNotFound(): Unit = {
+    val str = "Hello World"
+    val expected = List(str)
+
+    assertEquals(expected, str.splitAsList(','))
+  }
+
+  @Test
+  def splitAsListSingleDelimiter(): Unit = {
+    val str = "Hello,World"
+    val expected = List("Hello", "World")
+
+    assertEquals(expected, str.splitAsList(','))
+  }
+
+  @Test
+  def splitAsListMultipleDelimiters(): Unit = {
+    val str = "Hello,World,Good,Bye,World"
+    val expected = List("Hello", "World", "Good", "Bye", "World")
+
+    assertEquals(expected, str.splitAsList(','))
+  }
+
+  @Test
+  def splitAsListEmptySubStrings(): Unit = {
+    val str = "Hello,,World,"
+    val expected = List("Hello", "World")
+
+    assertEquals(expected, str.splitAsList(','))
+  }
+
+  @Test
+  def splitAsListDelimiterAtTheEnd(): Unit = {
+    val str = "Hello,World,"
+    val expected = List("Hello", "World")
+
+    assertEquals(expected, str.splitAsList(','))
+  }
+
+  @Test
+  def splitAsListDelimiterAtTheBeginning(): Unit = {
+    val str = ",Hello,World"
+    val expected = List("Hello", "World")
+
+    assertEquals(expected, str.splitAsList(','))
+  }
+
+  @Test
+  def splitAsListPreserveEmptySubStrings(): Unit = {
+    val str = ",Hello,,World,"
+    val expected = List("", "Hello", "", "World", "")
+
+    assertEquals(expected, str.splitAsList(separator = ',', preserveEmptySubStrings = true))
+  }
+}